At present, International Telecommunication Union (ITU) proposes very stringent requirements to the next generation mobile communication system—International Mobile Telecommunications-Advanced (IMT-Advanced), for example, the maximum system bandwidth needs to reach 100 MHz and peak rate of uplink and downlink data transmission respectively need to reach 1 Gbps and 500 Mbps. Also, it proposes very high requirements to cell spectral efficiency of system, especially to edge spectral efficiency.
In order to meet the requirements of IMT-Advanced system, 3rd Generation Partnership Project (3GPP) proposes Coordinated Multi-Point Operation (CoMP) technology to improve system performance in its next generation mobile cellular communication system, i.e. Long Term Evolution Advanced (LTE-Advanced).
Coordinated Multi-Point Operation (CoMP) technology is the cooperation among multiple transmission points which are geographically separated from each other. CoMP technology includes downlink coordinated transmission and uplink joint reception, while downlink coordinated transmission includes coordinated scheduling solution and coordinated transmission solution. Therein, in the coordinated scheduling solution, with coordination of time, frequency and space resources between cells, base station allocates mutually orthogonal resources to different user equipments (UE), to avoid the interference between them, reduce the interference between cells, and thereby improve edge performance; in the coordination transmission solution, multiple cells transmit data to one UE on the same time/frequency resources, to strengthen the signal received by UE, that could improve the quality of the signal received by UE according to the superposition of useful signals from the multiple cells, also reduce interference suffered by UE, and thereby improve system performance; uplink joint reception means that multiple cells receive data from one UE so that joint reception can be done at the base station to improve demodulation quality of data.
In the existing LTE system, UE sends uplink Sounding Reference Signals (SRS) to evolved Node-B (eNodeB) on time/frequency resources assigned by its serving cell, the eNodeB estimates the channel state information (CSI) between the UE and the eNodeB according to received SRS, and applies the estimated CSI for uplink frequency scheduling, Modulation and Coding Scheme (MCS) choosing and resources allocation. To Time Division Duplex (TDD) system, eNodeB also could calculate weighted vector of downlink beamforming according to the achieved uplink channel state information.
In the process of implementing the present invention, the inventor discovers that the existing technology has at least the following problems:
In the existing LTE system, the unit of SRS resource allocation is assigned by its serving cell, eNodeB allocates mutually orthogonal resources to different UEs intra-cell, while SRS of neighboring cells could be allocated in different sub-frames for transmission. At the same time, SRS base sequence is bound to the cell ID of the serving cell, that is to say, the eNodeB and the UE could get the base sequence in case that the eNodeB and the UE all get the serving cell ID. But in LTE-Advanced system, when CoMP SRS base sequence used in CoMP SRS cluster is not bound to the serving cell ID, the UE could not get the SRS sequence information.